break one's arm patting oneself on the back

verb1

•
(humorous) To be very full of oneself. Often used as a sarcastic caution: "don't break your arm patting yourself on the back".
- — We're the best football team in the state! — Careful, dude, don't break your arm patting yourself on the back.

forms

broke one's arm patting oneself on the back · broken one's arm patting oneself on the back · breaking one's arm patting oneself on the back · breaks one's arm patting oneself on the back